Parsing of table content

[Vitaliy-1]

Algorithms for table parsing. Inspired by: http://ieg.ifs.tuwien.ac.at/projects/pdf2table/yildiz_iicai05.pdf
Particularly, I've implemented the first algorithm from there and the idea in general. I suppose it's called the line-based approach. It works much better than tabula, as a minimum on my test instance.
related to:
#514
#340
Examples: https://vitaliy-1.github.io/tablesExample/

[coveralls]

Coverage increased (+0.5%) to 37.788% when pulling ca98798 on Vitaliy-1:master-tables into 53044fd on kermitt2:master.

[kermitt2]

Awesome work @Vitaliy-1 ! I've processed a couple thousand PDF and looked at a few of them. Tables look often very good. The main issue I think, as you noted in your examples, is when the table notes are added in the last line of the table. Possibly we could introduce an additional label in the table model to label those table notes explicitly to get them removed from the table content. What do you think?

Thanks a lot for the contribution!